The project is devoted to research in clinical hypertension. Pathogenesis of clinical hypertension will be assessed to two areas. The role of the renin-angiotensin system will be studied through measurement of plasma renin activity (PRA), plasma renin substrate (PRS) and hemodynamic responses during infusion of a specific angiotensin II antagonist, saralasin. In particular, hypertension associated with glucocorticoid excess and coarctation of the aorta will be evaluated. The action of prostaglandin A1 (PGA1) infusion upon hemodynamic and renal function in hypertensive patients will be explored. The effect of renin status and endogenous prostaglandin synthesis as determinants of the action of infused PGA1 will be assessed. Special attention will be paid to the effect of aspirin upon sodium balance, PRA and renal function. BIBLIOGRAPHIC REFERENCES: Krafoff, L.R., Vlachakis, N.D., Mendlowitz, M. and Stricker, J.: Differential effect of prostaglandin A1 in low, normal and high renin hypertensive patients. Clin. Science 48: Suppl.2: 3110313, 1975. Ribeiro, A.B. and Krakoff, L.R.: Angiotensin blockade in coarctation of the aorta. The New Engl. J. of Med. 295: 148-150, 1976.